Flexible Zn-ion batteries based on manganese oxides: Progress and prospect

The ever-growing market of wearable electronic devices has greatly stimulated the rapid development of flexible Zn-ion batteries(ZIBs).Manganese oxides are one of the most commonly used hosts for zinc ion accommodation and thus receive particular research interest for high-performance flexible ZIB constructions.In this review,a comprehensive summary of the recent development of flexible ZIBs with manganese oxides as cathode materials is presented.Apart from the brief introduction of flexible electronic devices and ZIBs,the charge storage mechanisms and crystal structures of various manganese oxides are summarized.Modifications of the cathode materials in terms of morphology,conductivity,structures,and flexibilities are illustrated in detail,together with the demonstration of structure-performance relationships and applications in flexible ZIBs.Finally,limitations to be overcome are indicated and the future work directions are proposed.

Roles of Ceria on Copper and Manganese Oxides Catalyst——Adsorption of NO and CO

A microreactor system and TPD techniques were used to study the reaction kinetics of the CO+ NO reaction and the adsorption of CO,NO,CO_2 and N_2O over Cu-Mn-O(Ⅰ)and Cu-Mn-Ce-O(Ⅱ) catalysts.The results show that the catalytic activity of(Ⅱ)is higher than that of(Ⅰ)for the CO+NO reac- tion,and the higher the conversion of NO,the larger was the activity difference between(Ⅰ)and(Ⅱ).For (Ⅰ)the rate of NO elimination is dependent on the partial pressures of NO,CO,CO_2 with the kinetics or- ders of 0.48,0.56,0.08,respectively.The TPD study shows that the presence of Ce in(Ⅱ)may promote the adsorption of NO,CO on the surface,i.e.an increase of the coverage θ_(NO),θ_(CO),which result in a decrease of the hindrance of the reaction products.For CO_2 and N_2O the situation is in the opposite,the presence of Ce makes the θ_(CO)_2)and θ_(NO)on(Ⅱ)decrease,which weakens the inhibition of CO_2 for the reaction.

MnO Stabilized in Carbon-Veiled Multivariate Manganese Oxides as High-Performance Cathode Material for Aqueous Zn-Ion Batteries

Aqueous Zn-ion battery has emerged as one of the most prospective energy storage devices due to its low cost,high safety,and eco-friendliness.However,Zn-ion batteries are bottlenecked by significant capacity fading during long-term cycling and poor performance at high current rates.Here,we report an available cooperation of multivariate manganese oxides@carbon hybrids(MnO_(2)/MnO@C and MnO_(2)/Mn_(3)O_(4)@C)via a plasma-assisted design as an attractive Zn-ion cathode.Among them,the MnO_(2)/MnO@C cathode exhibits a reversible specific capacity of 165 m Ah g^(-1)over 200 cycles at a high rate of 0.5 A g^(-1),and possesses great rate performance with high capacities of 110 and 100 m Ah g^(-1)at a high rate of 0.8 and 1 A g^(-1),respectively.The good cathode performance significantly results from the facile charge transfer and ions(Zn^(2+)and H^(+))insertion in the manganese oxides/carbon hybrids featuring phase stability behavior in the available cooperation of multivalence and carbon conductive substrates.This work will promote the Zn-manganese dioxide system for the design of low-cost and high-performance aqueous rechargeable Zn-ion batteries.

Critical role of corrosion inhibitors modified by silyl ether functional groups on electrochemical performances of lithium manganese oxides

Lithium manganese oxides(Li Mn2 O4, LMO) have attracted significant attention as important cathode materials for lithium-ion batteries(LIBs), which require fast charging based on their intrinsic electrochemical properties. However, these properties are limited by the rapid fading of cycling retention, particularly at high temperatures, because of the severe Mn corrosion triggered by the chemical reaction with fluoride(F-) species existing in the cell. To alleviate this issue, three types of silyl ether(Si–O)-functionalized task-specific additives are proposed, namely methoxytrimethylsilane, dimethoxydimethylsilane, and trimethoxymethylsilane. Ex-situ NMR analyses demonstrated that the Si-additives selectively scavenged the F-species as Si forms new chemical bonds with F via a nucleophilic substitution reaction due to the high binding affinity of Si with F-, thereby leading to a decrease in the F concentration in the cell. Furthermore, the addition of Si-additives in the electrolyte did not significantly affect the ionic conductivity or electrochemical stability of the electrolyte, indicating that these additives are compatible with conventional electrolytes. In addition, the cells cycled with Si-additives exhibited improved cycling retention at room temperature and 45 °C. Among these candidates, a combination of MTSi and the LMO cathode was found to be the most suitable choice in terms of cycling retention(71.0%), whereas the cell cycled with the standard electrolyte suffered from the fading of cycling retention triggered by Mn dissolution(64.4%). Additional ex-situ analyses of the cycled electrodes using SEM, TEM, EIS, XPS, and ICP-MS demonstrated that the use of Si-additives not only improved the surface stability of the LMO cathode but also that of the graphite anode, as the Si-additives prevent Mn corrosion. This inhibits the formation of cracks on the surface of the LMO cathode, facilitating the formation of a stable solid electrolyte interphase layer on the surface of the graphite anode. Therefore, Si-additives modified by Si–O functional groups can be effectively used to increase the overall electrochemical performance of the LMO cathode material.

Lead and Cadmium Adsorption onto Iron Oxides and Manganese Oxides in the Natural Surface Coatings Collected on Natural Substances in the Songhua River of China

Natural surface coatings collected from natural substances （NSCsNS） were employed to study the roles of the main chemical components （iron oxides, manganese oxides, and other components） in controlling the adsorption of lead（Pb） and cadmium（Cd） in aquatic environments. The selective chemical extraction followed by the adsorption of Pb and Cd experiments and statistical analysis, were used to investigate the adsorption property of each component. Hydroxylamine hydrochloride was used to remove manganese oxides selectively, and sodium dithionite was used to extract iron oxides and manganese oxides. The result indicated that iron oxides and manganese oxides played an important role in the adsorption of Pb and Cd on NSCsNS, and the relative contribution was about two-thirds. The contribution of manganese oxides was the greatest, with a lesser role indicated for other components. The adsorption ability of manganese oxides for Pb and Cd was greater than that of iron oxides or other components for Pb and Cd. The Pb adsorption observed in each component was greater than Cd adsorption.

Citrate-promoted dissolution of nanostructured manganese oxides:Implications for nano-enabled sustainable agriculture

Nanostructured manganese oxides (nano-MnO_(x)) have shown great promises as versatile agrochemicals in nano-enabled sustainable agriculture,owing to the coupled benefits of controlled release of dissolved Mn2+,an essential nutrient needed by plants,and oxidative destruction of environmental organic pollutants.Here,we show that three δ-MnO_(2)nanomaterials consisting of nanosheet-assembled flower-like nanospheres not only exhibit greater kinetics in citrate-promoted dissolution,but also are less prone to passivation,compared with three α-MnO_(2)nanowire materials.The better performance of the δ-MnO_(2)nanomaterials can be attributed to their higher abundance of surface unsaturated Mn atoms–particularly Mn(Ⅲ)–that is originated from their specific exposed facets and higher abundance of surface defects sites.Our results underline the great potential of modulating nanomaterial surface atomic configuration to improve their performance in sustainable agricultural applications.

Cerium-modified amorphous manganese oxides for efficient catalytic removal of ozone

Manganese-based catalysts were widely developed for catalytic removal of ozone,and the low stability and water inactivation are major challenges.To improve removal performance of ozone,three methods were applied to modify amorphous manganese oxides,including acidification,calcination and Ce modification.The physiochemical properties of prepared samples were characterized,and the catalytic activity for ozone removal was evaluated.All modification methods can promote the removal of ozone by amorphous manganese oxides,and Ce modification showed the most significant enhancement.It was confirmed that the introduction of Ce markedly changed the amount and property of oxygen vacancies in amorphous manganese oxides.Superior catalytic activity of Ce-MnO_(x) can be ascribed to its more content and enhanced formation ability of oxygen vacancies,larger specific surface area and higher oxygen mobility.Furthermore,the durability tests under high relative humidity(80%)determined that Ce-MnO_(x) showed excellent stability and water resistance.These demonstrate the promising potential of amorphously Ce-modified manganese oxides for catalytic removal of ozone.

Highly efficient removal of ozone by amorphous manganese oxides synthesized with a simple hydrothermal method

Amorphous manganese oxides (MnO_(x)) were synthesized by facile hydrothermal reactions between potassium permanganate and manganese acetate.Synthesis parameters,including hydrothermal time and temperature and molar ratio of precursors,significantly affected the ozone removal performance and structure property of MnO_(x).Amorphous MnO_(x)-1.5,which was prepared at the Mn^(2+)/Mn^(7+)molar ratio of 1.5 under hydrothermal conditions of 120℃ and 2 hr,showed the highest ozone removal rate of 93% after 480 min at the room temperature,RH (relative humidity)=80%and WHSV (weight hourly space velocity)=600 L/(g·hr).The morphology,composition and structure of catalysts were investigated with X-ray diffractometer (XRD),Raman spectra,N_(2) physisorption,field emission scanning electron microscope (FESEM),X-ray photoelectron spectroscopy (XPS),H2temperature-programmed reduction (H_(2)-TPR),O_(2) temperature-programmed desorption (O_(2)-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS).It was confirmed that high catalytic activity of amorphous MnOxfor ozone removal was mainly ascribed to its abundant oxygen vacancies,high oxygen mobility and large specific surface area.

Stable 4.5 V LiCoO_(2)cathode material enabled by surface manganese oxides nanoshell

Charging the LiCoO_(2)(LCO)cathode to a higher voltage,for example 4.5 V compared to the commonly used 4.2 V,is now intensively pursued so as to achieve a higher specific capacity.However,it suffers severe surface structural degradation and detrimental interfacial side reactions between cathode and electrolyte,which lead to the fast capacity fading during long-term cycling.Here,a surface coating strategy was developed for the protection of 4.5 V LCO by constructing a manganese oxides(MOs)nanoshell around LCO particles,which was achieved through a solution-based coating process with success in controlling the growth kinetics of the coating species.We found that the introduction of the MOs nanoshell is highly effective in alleviating the organic electrolyte decomposition at the cathode surface,thus ensuring a much more stable LiF-rich cathode-electrolyte interface and an obvious lower interfacial resistance during electrochemical cycling.Meanwhile,this protection layer can effectively improve the structural stability of the cathode by hindering the cracks formation and structural degradation of LCO particles.Therefore,the MOs modified LCO exhibited excellent rate performance and a high discharge capacity retention of 81.5%after 100 cycles at 1 C compared with the untreated LCO(55.2%),as well as the improved thermal stability and cyclability at the elevated temperature.It is expected that this discovery and fundamental understanding of the surface chemistry regulation strategy provide promising insights into improving the reversibility and stability of LCO cathode at the cut-off voltage of 4.5 V.

Preparation of Manganese Oxide and Its Adsorption Properties

The in-situ oxidation of manganese sulfate solution with H2O_(2),sodium hypochlorite,potassium permanganate and oxygen as oxidants was investigated by means of SEM,EDS,XRD,BET and infrared analysis,and the effects of different oxidants on the morphology,phase composition,surface properties and specific surface area of manganese oxides were investigated.The experimental results show that the diameter of manganese oxide particles prepared with H_(2)O_(2)is the smallest,about 50 nm,and the specific surface area is the largest,63.8764 m^(2)/g.It has the advantages of abundant surface hydroxyl groups,no introduction of other impurities and large adsorption potential.It is most suitable to be used as an oxidant for oxidizing manganese sulfate solution to prepare manganese oxide by in-situ oxidation.Nano manganese oxide prepard by H_(2)O_(2)in-situ oxidation method is used as adsorbent to adsorb cobalt and nickel impurities in manganese sulfate.When the reaction pH is 6,the reaction time is 30min and the amount of adsorbent is 1.0 g,the adsorption rates of cobalt and nickel impurities in 100ml manganese sulfate solution are 97.59%and 97.67%,respectively.The residual amounts of cobalt and nickel meet the industrial process standard of first-class products(Co,Ni w/%≤0.005)of high-purity manganese sulfate(Hg/t4823-2015)for batteries.The study plays a guiding role in the preparation and regulation of manganese oxide,and provides a new method with high efficiency,purity and adsorbent availability for the preparation of high-purity manganese sulfate solution.

Roles of manganese oxides in degradation of phenol under UV-Vis irradiation:Adsorption,oxidation,and photocatalysis

Manganese oxides are known as one type of semiconductors,but their photocatalysis characteristics have not been deeply explored.In this study,photocatalytic degradation of phenol using several synthesized manganese oxides,i.e,acidic birnessite （BIR-H）,alkaline birnessite （BIR-OH）,cryptomelane （CRY） and todorokite （TOD）,were comparatively investigated.To elucidate phenol degradation mechanisms,X-ray diffraction （XRD）,ICP-AES （inductively coupled plasma-atomic emission spectroscopy）,TEM （transmission electronic microscope）,N 2 physisorption at 77 K and UV-visible diffuse reflectance spectroscopy （UV-Vis DRS） were employed to characterize the structural,compositional,morphological,specific surface area and optical absorption properties of the manganese oxides.After 12 hr of UV-Vis irradiation,the total organic carbon （TOC） removal rate reached 62.1%,43.1%,25.4%,and 22.5% for cryptomelane,acidic birnessite,todorokite and alkaline birnessite,respectively.Compared to the reactions in the dark condition,UV- Vis exposure improved the TOC removal rates by 55.8%,31.9%,23.4% and 17.9%.This suggests a weak ability of manganese oxides to degrade phenol in the dark condition,while UV-Vis light irradiation could significantly enhance phenol degradation.The manganese minerals exhibited photocatalytic activities in the order of：CRY BIR-H TOD BIR-OH.There may be three possible mechanisms for photochemical degradation：（1） direct photolysis of phenol;（2） direct oxidation of phenol by manganese oxides;（3） photocatalytic oxidation of phenol by manganese oxides.Photocatalytic oxidation of phenol appeared to be the dominant mechanism.

Catalytic activity of porous manganese oxides for benzene oxidation improved via citric acid solution combustion synthesis

Various manganese oxides(MnOx) prepared via citric acid solution combustion synthesis were applied for catalytic oxidation of benzene. The results showed the ratios of citric acid/manganese nitrate in synthesizing process positively affected the physicochemical properties of MnOx, e.g., BET(Brunauer-Emmett-Teller) surface area, porous structure, reducibility and so on, which were in close relationship with their catalytic performance. Of all the catalysts, the sample prepared at a citric acid/manganese nitrate ratio of 2:1(C2M1) displayed the best catalytic activity with T(90)(the temperature when 90% of benzene was catalytically oxidized) of 212 ℃. Further investigation showed that C2M1 was Mn2O3 with abundant nano-pores, the largest surface area and the proper ratio of surface Mn^4+/Mn^3+, resulting in preferable low-temperature reducibility and abundant surface active adsorbed oxygen species. The analysis results of the in-situ Fourier transform infrared spectroscopy(in-situ FTIR) revealed that the benzene was successively oxidized to phenolate, o-benzoquinone, small molecules(such as maleates, acetates, and vinyl), and finally transformed to CO2 and H2O.

Metal-organic framework loaded manganese oxides as efficient catalysts for low-temperature selective catalytic reduction of NO with NH3

A mild in-situ deposition method was used to fabricate Mn-based catalysts on a UiO-66 carder for the selective catalytic reduction of NO by NH3 （NH3-SCR）. The catalyst with 8.5 wt-% MnOx loading had the highest catalytic activity for NH3-SCR with a wide temperature window （100-290 C） for 90% NO conversion. Char- acterization of the prepared MnOx/UiO-66 catalysts showed that the catalysts had the crystal structure and porosity of the UiO-66 carrier and that the manganese particles were well-distributed on the surface of the catalyst. X-ray photoelectron spectroscopy analysis showed that there are strong interactions between the MnOx and the Zr oxide secondary building units of the UiO-66 which has a positive effect on the catalytic activity. The 8.5 wt-% MnOx catalyst maintained excellent activity during a 24-h stability test and exhibited good resistance to SO2 poisoning.

Controlled synthesis of porous spinel cobalt manganese oxides as efficient oxygen reduction reaction electrocatalysts

In this article, we report a facile precursor pyrolysis method to prepare porous spinel-type cobalt manganese oxides （CoxMng-xO4） with controllable morphologies and crystalline structures. The capping agent in the reaction was found to be crucial on the formation of the porous spinel cobalt manganese oxides from cubic Co2MnO4 nanorods to tetragonal CoMn2O4 microspheres and tetragonal CoMn204 cubes, respectively. All of the prepared spinel materials exhibit brilliant oxygen reduction reaction （ORR） electrocatalysis along with high stability. In particular, the cubic Co2MnO4 nanorods show the best performance with an onset potential of 0.9 V and a half-wave potential of 0.72 V which are very close to the commercial Pt/C. Meanwhile, the cubic Co2MnO4 nanorods present superior stability with negligible degradation of their electrocatalytic activity after a continuous operation time of 10,000 seconds, which is much better than the commercial Pt/C electrocatalvst.

Catalytic Amidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxamide over Alkali Manganese Oxides

2,5-Furandicarboxamide was firstly synthesized in yield of 85% via catalytic oxidative amidation of 5-hydroxy- methylfurfural with aqueous NH3 over alkali manganese oxides of a-MnO2/NaxMnO〉 The intermediates of 5-hydroxymethyl-furonitrile, 2,5-dicyanofuran, and 5-cyano-2-furancarboxamide were verified and their reactivities were further examined. The kinetic analysis results showed that the transformation of intermediate product of 5-cyano-2-furancarboxamide to 2,5-furan-dicarboxamide is a slower step, which is closely relative to the reaction temperature and basicity of catalyst.

Redox reactions of iron and manganese oxides in complex systems

Conspectus:Redox reactions of Fe-and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments.Due to experimental and analytical challenges associated with complex environments,there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems,and most of the studies so far have only focused on simple model systems.To bridge the gap between simple model systems and complex environmental systems,it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation.In this Account,we primarily focused on(1)the oxidative reactivity of Mn-and Fe-oxides and(2)the reductive reactivity of Fe(Ⅱ)/iron oxides in comolex model systems toward contaminant degradation.The effects of common metal ions such as Mn2+,Ca2+,Ni2+,Cr3+and Cu2+,ligands such as small anionic ligands and natural organic matter(NOM),and second metal oxides such as A1,Si and Ti oxides on the redox reactivity of the systems are briefly summarized.

Methane Oxidation on the Surfaces of Manganese Oxides:a First Principles Study

A comprehensive density functional theory calculation was employed to investigate the possible reaction pathways and mechanisms of methane complete oxidation(CH4+2O2→CO2+2H2O)on different manganese oxides including a-MnO2(100)and b-MnO2(111)surfaces.According to a coupling of the Mars-van Krevelen and Langmuir-Hinshelwood mechanism,the activation energy barrier and the reaction energy of each elementary surface reaction were determined.Our calculated results show that the detailed processes for methane oxidation on two surfaces are different due to the differences in the surface structure.The breaking of the last C–H bond of CH4 moleculeis the rate-determining step with an activation barrier of 0.85 eV for a-MnO2(100)surface.By contrast,the overall reaction rate on b-Mn O2(111)surface is limited by the dissociation of the second O2 molecule adsorbed on the vacancy site,and re-oxidation of the reduced b-MnO2(111)surface by the gaseous oxygen requires a much higher energy barrier of 1.44 eV.As a result,the a-Mn O2(100)exhibits superior activity and durability in the methane oxidation reaction than b-MnO2(111)surface.The present study provides insight into understanding the structure-catalytic activity relationship of the catalysts based on manganese oxides towards the methane oxidation reaction.

Defect-induced deposition of manganese oxides on hierarchical carbon nanocages for high-performance lithium-oxygen batteries

The cathode of lithium-oxygen(Li-O_(2))batteries should have large space for high Li_(2)O_(2) uptake and superior electrocatalytic activity to oxygen evolution/reduction for long lifespan.Herein,a high-performance MnO_(x)/hCNC cathode was constructed by the defect-induced deposition of manganese oxide(MnOx)nanoparticles on hierarchical carbon nanocages(hCNC).The corresponding Li-O2 battery(MnOx/hCNC@Li-O_(2))exhibited excellent electrocatalytic activity with the low overpotential of 0.73-0.99 V in the current density range of 0.1-1.0 A·g^(-1).The full discharge capacity and cycling life of MnO_(x)/hCNC@Li-O_(2) were increased by~86.7%and~91%,respectively,compared with the hCNC@Li-O_(2) counterpart.The superior performance of MnO_(x)/hCNC cathode was ascribed to(i)the highly dispersed MnO_(x) nanoparticles for boosting the reversibility of oxygen evolution/reduction reactions,(ii)the interconnecting pore structure for increasing Li_(2)O_(2) accommodation and facilitating charge/mass transfer,and(iii)the concealed surface defects of hCNC for suppressing side reactions.This study demonstrated an effective strategy to improve the performance of Li-O_(2) batteries by constructing cathodes with highly dispersed catalytic sites and hierarchical porous structure.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

An amorphous manganese iron oxide hollow nanocube cathode for aqueous zinc ion batteries

Aqueous zinc ion batteries(ZIBs) are attracting considerable attentions for practical energy storage because of their low cost and high safety.Nevertheless,the traditional manganese oxide cathode materials suffer from the low intrinsic electronic conductivity,sluggish ions diffusion kinetics,and structural collapse,hindering their large-scale application.Herein,we successfully developed a latent amorphous Mn_(1.8)Fe_(1.2)O_(4) hollow nanocube(a-H-MnFeO) cathode material derived from Prussian blue analogue precursor.The amorphous nature endows the cathode with lower diffusion barrier and narrower band gap compared with crystalline counterpart,resulting in the superior Zn^(2+) ions and electrons transport kinetics.Hollow structure can furnish abundant surface sites and suppress the structural collapse during the repeated charge/discharge processes.By virtue of the multiple advantageous features,the a-H-MnFeO cathode exhibits exceptional electrochemical performance,in terms of high capacity,excellent rate capability,and prolonged cycle life.This strategy will pave the way for the structural design of emerging cathode materials.